Molten-Salt Electrochemical Preparation of Co 2 B/MoB 2 Heterostructured Nanoclusters for Boosted pH-Universal Hydrogen Evolution.

Boosting the hydrogen evolution reaction (HER) activity of α-MoB 2 at large current densities and in pH-universal medium is significant for efficient hydrogen production. In this work, Co 2 B/MoB 2 heterostructured nanoclusters are prepared by molten-salt electrolysis (MSE) and then used as a HER catalyst. The composition, structure, and morphology of Co 2 B/MoB 2 can be modulated by altering the stoichiometries of raw materials and synthesis temperatures. Impressively, the obtained Co 2 B/MoB 2 at optimized conditions exhibits a low overpotential of 297 and 304 mV at 500 mA cm -2 in 0.5 m H 2 SO 4 and 1 m KOH, respectively. Moreover, the Co 2 B/MoB 2 catalyst possesses a long-term catalytic stability of over 190 h in both acidic and alkaline medium. The excellent HER performance is due to the modified electronic structure at the Co 2 B/MoB 2 heterointerface where electrons are accumulated at the Mo sites to strengthen the H adsorption. Density functional theory (DFT) calculations reveal that the formation of the Co 2 B/MoB 2 heterointerface decreases the H adsorption and H 2 O dissociation free energies, contributing to the boosted HER intrinsic catalytic activity of Co 2 B/MoB 2 . Overall, this work provides an experimental and theoretical paradigm for the design of efficient pH-universal boride heterostructure electrocatalysts.